The present invention relates to a vertical engine including a crankshaft supported to be directed vertically.
In general, in a vertical engine including a crankshaft supported to be directed vertically in an engine block, a cylinder head-coupled surface for coupling a cylinder head and an oil pan-coupled surface for coupling an oil pan are formed on the engine block. Japanese Utility Model Application Laid-open No.64-25415 describes a vertical engine in which an end edge of an oil pan-coupled surface is positioned at a location short of a line extending downwards from a cylinder head-coupled surface, and Japanese Patent Application Laid-open No.8-100707 describes a vertical engine in which an oil pan-coupled surface is formed over a lower surface of an engine block and a lower surface of a cylinder head.
It should be noted here that the vertical engine described in the above Japanese Utility Model Application Laid-open No.64-25415 suffers from a problem that the area of the oil pan-coupled surface is insufficient, resulting in a limited volume of the oil pan, because the end edge of the oil pan-coupled surface is positioned at the location short of the line extending downwards from the cylinder head-coupled surface. The vertical engine described in the above Japanese Patent Application Laid-open No.8-100707 suffers from a problem that because the oil pan-coupled surface is formed over the lower surface of the engine block and the lower surface of the cylinder head, a flat coupled surface must be formed by a common machining, including a gasket between the engine block and the cylinder head, thereby causing an increase in machining cost. Moreover, special machining equipment capable of machining the hard gasket is required.
In a vertical engine in which an exhaust gas passage, a cooling-water passage, a drainage passage and the like extending vertically are provided in an oil pan forming member having an oil pan integrally provided therein, openings in the passages and an opening in the oil pan interfere with each other and for this reason, not only the position of the opening in the oil pan but also the volume of the oil pan is limited. Especially, in a vertical engine in which cooling-water passages are defined on opposite sides of a cylinder bore, it is necessary to provide a water-dispensing portion in the oil pan forming member for dispensing cooling water to each of the cooling-water passages on the opposite sides of the cylinder bore, and the position of the opening in the oil pan and the volume of the oil pan are further limited by the water-dispensing portion.
In general, an engine block forming a body of an engine is divided into two components: a cylinder block and a crankcase at a parting plane including the axis of a crankshaft, and the crankshaft is supported so as to be sandwiched between the cylinder block and the crankcase.
A single-cylinder vertical engine described in Japanese Patent Application Laid-open No.4-362231 is comprised of an engine block including an engine body integrally provided with a cylinder bore and a crankcase, and an upper cover which closes an opening in an upper surface of the engine block. A lower journal of the crankshaft is supported in a bearing bore provided in the engine block, and an upper journal of the crankshaft is supported in a bearing bore provided in the upper cover.
It should be noted here that if the engine block is divided into the cylinder block and the crankcase at the parting plane including the axis of the crankshaft, the bearing bores supporting the journals of the crankshaft are defined astride the cylinder block and the crankcase and hence, it is necessary to make the bearing bores by a common machining in a state in which the cylinder block and the crankcase have been temporarily coupled to each other. For this reason, the following problem is encountered: Steps of coupling and separating the cylinder block and the crankcase to and from each other are required, resulting in an increase in machining cost, and moreover, the cylinder block and the crankcase which were made by the common machining must be used in a set, resulting in a poor interchangeability of the components.
In the single-cylinder vertical engine described in Japanese Patent Application Laid-open No.4-362231, the oil supplied from an oil pump mounted in the cylinder block to the bearing bore of the lower journal of the crankshaft is supplied through an oil passage defined in the crankshaft to a crankpin portion supporting a connecting rod and then through an oil passage defined in the crankshaft to the bearing bore of the upper journal. Therefore, especially in the case of a multi-cylinder engine, the following problem is encountered: the structure of the oil passage in the crankshaft is complicated, and moreover, it is difficult to supply a sufficient amount of oil to the bearing bore of the upper journal of the crankshaft.
The present invention has been accomplished with the above circumstances in view, and it is a first object of the present invention to increase the volume of an oil pan coupled to an oil pan-coupled surface formed on a lower surface of an engine block by a simple structure in a vertical engine including a crankshaft supported to be directed vertically.
It is a second object of the present invention to enhance the workability and lubricatability of the bearing bores of journals of the crankshaft in the vertical engine.
To achieve the above first object, according to the present invention, there is provided a vertical engine comprising an engine block including a cylinder bore integrally provided therein and a crankshaft supported to be directed vertically, a cylinder head coupled to a cylinder head-coupled surface vertically formed on the engine block, and an oil pan coupled to an oil pan-coupled surface horizontally formed on the engine block, wherein the oil pan-coupled surface extends below the cylinder head beyond a line extending downwards from the cylinder head-coupled surface.
With the above arrangement, the oil pan-coupled surface formed on the engine block extends below the cylinder head beyond the line extending downwards from the cylinder head-coupled surface. Therefore, the area of the oil pan-coupled surface can be increased without interference with the cylinder head-coupled surface, and the volume of the oil pan coupled to the oil pan-coupled surface can be increased. Moreover, the cylinder head-coupled surface and the oil pan-coupled surface are not continuous with each other and hence, there is no possibility that the sealing of the coupled surfaces may be impeded.
An oil case-coupled surface 115 in each of the embodiments corresponds to the oil pan-coupled surface of the present invention.
To achieve the above first object, in addition to the above arrangement, there is a provided a vertical engine including the above-described arrangement, wherein an oil pan forming member having the oil pan integrally provided therein is integrally formed with a peripheral wall of a main exhaust passage.
With the above arrangement, the peripheral walls of the main exhaust passages are integrally formed on the oil pan forming member. Therefore, the main exhaust passages can be displaced toward the cylinder head without recourse to mating surfaces of the engine block and the cylinder head. As a result, the area of an opening in the oil pan can be increased, leading to an increased volume of the oil pan.
To achieve the above first object, in addition to the above arrangement, there is provided a vertical engine wherein the oil pan forming member is integrally formed with a peripheral wall of a cooling-water passage.
With the above arrangement, the peripheral walls of the cooling-water passages are integrally formed on the oil pan forming member. Therefore, the cooling-water passages can be displaced toward the cylinder head without recourse to mating surfaces of the engine block and the cylinder head. As a result, the area of an opening in the oil pan can be increased, leading to an increased volume of the oil pan.
To achieve the above second object, according to the present invention, there is provided a vertical engine having a crankshaft supported to be directed vertically, comprising an engine block which is formed by molding integrally with a cylinder bore and a crankcase and which has a bearing bore defined therein for supporting a lower journal of the crankshaft, an upper cover which is coupled to the engine block so as to close an opening in an upper surface of the engine block and which has a bearing bore defined therein for supporting an upper journal of the crankshaft, an oil pan coupled to a lower surface of the engine block, an oil pump for supplying an oil within the oil pan to portions to be lubricated, and an oil passage which is defined in the engine block and the upper cover and through which the oil discharged from the oil pump is supplied to the bearing bore for supporting the upper journal of the crankshaft.
With the above arrangement, the bearing bore for supporting the lower journal of the crankshaft is defined only in the engine block, and the bearing bore for supporting the upper journal of the crankshaft is defined only in the upper cover. Therefore, to make both of the bearing bores, it is not required that a common machining is conducted in a state in which two members have been coupled to each other. Thus, steps of coupling and separating the two members to and from each other are not required, leading to a reduction in machining cost, and also the engine block and the upper cover can be exchanged independently, leading to an enhanced interchangeability. Moreover, the supplying of the oil to the bearing bore of the upper journal of the crankshaft is conducted from the oil pump through the oil passages defined in the engine block and the upper cover. Therefore, the supplying of the oil is reliably achieved, and the structures of the oil passages are also simplified, as compared with a system in which the supplying of the oil to the bearing bore of the upper journal is conducted through an oil passage defined in the crankshaft.
To achieve the second object, in addition to the above arrangement, there is a provided a vertical engine wherein a most downstream portion of the oil passage defined in the upper cover comprises a blind bore provided at a location spaced obliquely and upwards apart from an inner peripheral surface of the bearing bore in the upper cover.
With the above arrangement, the most downstream portion of the oil passage in the upper cover comprises a blind bore provided at the location spaced obliquely and upwards apart from the inner peripheral surface of the bearing bore in the upper cover. Therefore, the blind bore can easily be made from the side of the lower surface of the upper cover, and moreover, it is unnecessary to provide a blind plug required when the most downstream oil passage is comprised of a through-bore extending from the outer surface of the upper cover to the inner peripheral surface of the bearing bore. This contributes to reductions in number of components and number of machining steps.